Jeh Johnson has led an illustrious career by any measure—having served as both U.S. secretary of Homeland Security and the general counsel for the U.S. Department of Defense, he’s been at the forefront of efforts against major threats against the United States.

So what, among these threats, does Johnson deem the most dangerous? As he put it: “I’d have to say cyber threats are the No. 1 threat to our nation.”